PersistentVolumeClaim (PVC) definition in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a PersistentVolumeClaim (PVC) in Kubernetes?

A PersistentVolumeClaim (PVC) is a request for storage by a user. It allows pods to claim storage resources without knowing the details of the underlying storage.

beginner

Which key fields are required in a basic PVC YAML definition?

apiVersion, kind, metadata (name), and spec (accessModes, resources.requests.storage).

intermediate

What does the accessModes field in a PVC specify?

It specifies how the volume can be mounted. Common values are ReadWriteOnce, ReadOnlyMany, and ReadWriteMany.

intermediate

How does a PVC relate to a PersistentVolume (PV)?

A PVC requests storage, and Kubernetes binds it to a matching PersistentVolume (PV) that provides the actual storage.

intermediate

What happens if no matching PersistentVolume is available for a PVC?

The PVC stays in a pending state until a suitable PersistentVolume is available or dynamically provisioned.

Which field in a PVC YAML defines the amount of storage requested?

A spec.resources.requests.storage

B metadata.name

C spec.accessModes

D apiVersion

The storage size requested is specified under spec.resources.requests.storage.

What does the access mode ReadWriteOnce mean in a PVC?

A The volume can be mounted as read-only by many nodes

B The volume can be mounted as read-write by a single node

C The volume can be mounted as read-write by many nodes

D The volume is read-only and cannot be mounted

ReadWriteOnce means the volume can be mounted as read-write by only one node at a time.

If a PVC is created but no matching PV exists, what is the PVC status?

A Available

B Bound

C Pending

D Released

The PVC remains in Pending state until a matching PV is found or provisioned.

Which Kubernetes object does a PVC bind to?

A Pod

B ConfigMap

C Namespace

D PersistentVolume (PV)

A PVC binds to a PersistentVolume (PV) that provides the actual storage.

What is the kind value in a PVC YAML file?

A PersistentVolumeClaim

B PersistentVolume

C StorageClass

D Pod

The kind field for a PVC YAML is PersistentVolumeClaim.

Explain the purpose of a PersistentVolumeClaim in Kubernetes and how it interacts with PersistentVolumes.

Think of PVC as a storage order and PV as the storage supply.

Describe the key fields in a PersistentVolumeClaim YAML and their roles.

Focus on the YAML structure and what each part means.

Practice

1. What is the main purpose of a PersistentVolumeClaim (PVC) in Kubernetes?

easy

A. To configure network policies

B. To define a container image for a pod

C. To schedule pods on specific nodes

D. To request storage resources from the cluster

Solution

1. Step 1: Understand PVC role

   A PVC is used to request storage resources in Kubernetes, separating storage use from storage details.

2. Step 2: Compare options

   Options A, B, and D relate to other Kubernetes features, not storage requests.

3. Final Answer:

   To request storage resources from the cluster -> Option D

4. Quick Check:

   PVC = Storage request [OK]

Hint: PVC always requests storage, not images or network [OK]

Common Mistakes:

• Confusing PVC with Pod or Deployment definitions
• Thinking PVC schedules pods
• Mixing PVC with network policies

2. Which of the following is the correct minimal YAML snippet to define a PVC requesting 5Gi of storage with ReadWriteOnce access mode?

easy

A. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadOnlyMany
resources:
requests:
storage: 5Gi

B. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 5Gi

C. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteMany
resources:
limits:
storage: 5Gi

D. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: my-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
cpu: 5Gi

Solution

1. Step 1: Check accessModes and storage request

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 5Gi correctly uses ReadWriteOnce and requests 5Gi storage under resources.requests.

2. Step 2: Identify errors in other options

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadOnlyMany resources: requests: storage: 5Gi uses ReadOnlyMany (not requested). apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteMany resources: limits: storage: 5Gi uses limits instead of requests. apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: cpu: 5Gi incorrectly requests cpu instead of storage.

3. Final Answer:

   Correct minimal PVC YAML with 5Gi and ReadWriteOnce -> Option B

4. Quick Check:

   accessModes + storage request = apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 5Gi [OK]

Hint: Use resources.requests.storage for size, accessModes for access [OK]

Common Mistakes:

• Using limits instead of requests for storage
• Wrong accessModes value
• Requesting cpu instead of storage

3. Given this PVC YAML snippet, what will be the requested storage size and access mode?

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data-pvc
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 10Gi
  storageClassName: fast-storage

medium

A. 10Gi storage with ReadWriteMany access

B. 10Gi storage with ReadWriteOnce access

C. 5Gi storage with ReadWriteMany access

D. 10Gi storage with ReadOnlyMany access

Solution

1. Step 1: Read storage size

   The YAML requests 10Gi storage under resources.requests.storage.

2. Step 2: Read access mode

   Access mode is ReadWriteMany as specified under accessModes.

3. Final Answer:

   10Gi storage with ReadWriteMany access -> Option A

4. Quick Check:

   storage=10Gi, access=ReadWriteMany [OK]

Hint: Check resources.requests.storage and accessModes list [OK]

Common Mistakes:

• Confusing ReadWriteOnce with ReadWriteMany
• Misreading storage size
• Ignoring storageClassName as it doesn't affect size or access

4. Identify the error in this PVC YAML snippet:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 2GB

medium

A. metadata name is missing

B. accessModes should be ReadOnlyMany

C. storage size unit should be Gi, not GB

D. apiVersion should be apps/v1

Solution

1. Step 1: Check storage size unit

   Kubernetes expects storage size units like Gi, Mi, not GB. '2GB' is invalid.

2. Step 2: Verify other fields

   accessModes and metadata name are correct. apiVersion for PVC is v1, not apps/v1.

3. Final Answer:

   storage size unit should be Gi, not GB -> Option C

4. Quick Check:

   Use Gi for storage size units [OK]

Hint: Use Gi, Mi units for storage size, not GB [OK]

Common Mistakes:

• Using GB instead of Gi for storage size
• Wrong apiVersion for PVC
• Changing accessModes unnecessarily

5. You want to create a PVC that requests 20Gi storage with ReadWriteOnce access and uses a storage class named "premium-ssd". Which YAML snippet correctly defines this PVC?

hard

A. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 20Gi
storageClassName: premium-ssd

B. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 20Gi
storageClassName: premium-ssd

C. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
limits:
storage: 20Gi
storageClassName: premium-ssd

D. apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: premium-pvc
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 20GB
storageClassName: premium-ssd

Solution

1. Step 1: Verify accessModes and storage size

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: premium-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 20Gi storageClassName: premium-ssd uses ReadWriteOnce and requests 20Gi storage correctly.

2. Step 2: Check storageClassName and units

   apiVersion: v1 kind: PersistentVolumeClaim metadata: name: premium-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 20Gi storageClassName: premium-ssd correctly sets storageClassName to premium-ssd and uses Gi units. Other options have wrong accessModes, use limits instead of requests, or wrong units (GB).

3. Final Answer:

   Correct PVC with 20Gi, ReadWriteOnce, and premium-ssd storage class -> Option A

4. Quick Check:

   accessModes=ReadWriteOnce + requests.storage=20Gi + storageClassName= premium-ssd [OK]

Hint: Use requests.storage with Gi units and correct accessModes [OK]

Common Mistakes:

• Using limits instead of requests for storage
• Wrong accessModes value
• Using GB instead of Gi for storage size